1. Field of the Invention
The present invention relates to a radio-corrected timepiece in which a time instant is corrected on the basis of a time instant information received through radio wave.
2. Description of the Prior Art
From old times, there has been developed the radio-corrected timepiece in which the time instant is automatically corrected by receiving a radio signal representing an accurate time instant.
At present, in each of the countries (for example, Germany, Japan, the United States of America, England and the like), there is sent out a long wave standard wave, in which a time instant information has been superimposed, from a radio station provided in a predetermined place.
In Japan, under the jurisdiction of the Ministry of Public Management, there is transmitted the long wave standard wave in which such a time instant information as shown by a time code of FIG. 9 has been superimposed.
In FIG. 9, the time instant information is transmitted with one minute being made one frame and, therein, values of day, hour, minute and the like being one-pulse-width-modulated for one bit, and a rise of a forefront pulse (reference marker M) in one frame accurately synchronizes with 0th second.
The aforesaid radio signal is generated in every one second, and it follows that, if it is generated for 0.2 second in one second, a position marker P is shown and, if it is generated for 0.5 second, one second is shown and, if it is generated for 0.8 second, 0 is shown.
This position marker P is contained in one frame by plural number and, as shown by P1–P0 in FIG. 9, is a signal appearing in a break for every 10 seconds of 0th second (exact second), 9th second, 19th second, 29th second, 39th second, 49th second, and 59th second. Only at 59th second and 0th second, this position marker P continuously appears in one frame and, between these two continuous position markers P, the later position maker is referred to as the reference marker M, and the reference marker M becomes a signal representing an exact minute position. Since a position of a signal representing the time instant and the like in the frame is determined with this exact minute position (i.e., the reference marker M) being made a reference, it is possible to take out a time instant data by performing a detection of this exact minute position.
In a recent quartz timepiece, an accuracy of about 20 seconds in error per month can be easily realized and, if it is supposed that a time instant correction is performed once in one month for instance, since the error of one minute or longer scarcely exists, usually it suffices if only a second correction is performed. Accordingly, usually it suffices if only a 0th second information can be received, and other information is unnecessary. Whereupon, there has been one in which a time instant correction is performed by a reception of the forefront pulse (reference marker M) in the frame synchronizing with the 0th second while corresponding to a lead/lag of a displayed time instant (refer to Patent Document 1).
However, also in the above conventional radio-corrected timepiece, a power source of a reception means must be made always ON till the reference marker M showing the forefront of the signal representing the exact minute position is detected and, in a case where the reference marker M could not be detected, the reception must be continued for some extent, so that there is a problem that a wasteful electric power consumption is used.
On the other hand, there is one in which the time instant is corrected by judging a bit number to be taken in from when a P code in one frame has been received (refer to Patent Document 2), but there are such problems that its processing becomes intricate, and a capacity of ROM storing a processing program increases.
Incidentally, also in the United States, like a time code shown in FIG. 10, similarly to our country, as to the time instant information one minute is made one frame, therein a time instant information such as day, hour and minute is contained, the rise of the forefront pulse (reference marker FRM) in one frame accurately synchronizes with 0th second, and there are contained plural position markers P (P1–P0) with a predetermined interval. Accordingly, in a case where the invention described in each of the Patent Documents is applied to a standard wave signal of FIG. 10, there are similar problems. Besides Japan and the United States, in the country where the standard wave signal having such a time instant information as shown in FIG. 9 and FIG. 10 is used, there arise problems similar to the above.
<Patent Document 1> Japanese Patent No. 2545662 Gazette
<Patent Document 2> Japanese Patent No. 2503376 Gazette
A problem of the present invention is to make the time instant correction possible while suppressing the electric power consumption due to the reception of the radio wave containing the time instant information.